1. Field of the Invention
The invention relates to printed circuit connectors in general and particularly to those connectors which must be polarized by means of a polarizing key to prevent the inadvertent insertion therein of printed circuit boards which would not function or might be damaged if mated with the wrong connector.
2. Description of the Prior Art
Printed circuit (p.c.) board edge receptacle connectors are well known in the art. Electrical conductors for various circuit elements on the p.c. board are located along an edge of the board. When the board is inserted into a receptacle connector, spring fingers within the connector make contact with the conductors on the p.c. board.
There is industry-wide standardization of p.c. board thickness, and contact width and spacing. Because of this standardization, it is possible to insert p.c. boards, each having different circuit elements and function, into the same p.c. board connector. If a p.c. board is inadvertently inserted into the wrong connector in an operating system, the board may be destroyed, for all practical purposes, and/or other faults may be engendered elsewhere in the system.
To overcome this potential problem, the typical p.c. board receptacle connector is capable of being keyed to prevent improper insertion of the wrong p.c. board in any given receptacle. Provision for keying usually takes the form of grooves between pairs of spring finger connectors, into which a polarizing key is inserted. Polarization is achieved by placing a cut-out, or slot at the edge of the p.c. board, which slot will accept the polarzing key when the board is inserted into its proper receptacle. Should an attempt be made to mis-mate a board and a receptacle, an interference results and insertion of the board is prevented.
Polarizing keys are relatively small items having dimensions on the order of 0.40 inches long, by 0.10 inches wide, by 0.3 inches thick.
Emplacement of this small device within the proper grooves in the receptacle connector is most commonly performed by manual operations which are error prone and time consuming. Typically, a needle-nose pliers or similar tool is used to grasp the polarizing key and insert it into the connector. Common errors comprise mis-placement of the key by insertion in the wrong location or mis-alignment of the key such that it is not everywhere equidistant from the spring fingers on either side. In the latter case, the cocked key prevents insertion of the p.c. board, even though the key is located at its assigned position within the receptacle.
These problems are inherent in such manual operations when the polarizing keys are inserted in the receptacles as a bench procedure. The task becomes even more tedious and prone to error in final assembly stages at which keys are inserted in receptacles in deep card bins or drawers or cabinets, or when a change is required in equipment operating in the field where interior cabinet areas may be dimly lit and have poor receptacle accessibility.
Another factor contributing to errors in locating the key in a receptacle is that the markings on the receptacle are small and difficult to read and do not relate directly to polarizer key location numbers.
The invention was conceived with the objects of simplifying emplacement of polarizer keys in p.c. board receptacle connectors, reducing the error rate, increasing productivity, and providing an easy means of locating and inserting the keys accurately regardless of whether the operation was performed at bench level assembly or at rack or drawer level.